Delivery status and reasons for failed delivery

Learn what the different message status ...

Learn what the different message status mean as well as the most common reasons for a failed delivery. Avoid that your SMS messages are blocked by carriers by following best practises.

What does the delivery status of my SMS messages mean?

ENROUTE:

The message has been sent to a mobile ne...

The message has been sent to a mobile network, and is on its way to its final destination.

DELIVERED:

The end user’s mobile device has confirm...

The end user’s mobile device has confirmed the delivery, and if the message is charged, the charge was successful.

EXPIRED:

The message has exceeded its validity pe...

The message has exceeded its validity period without getting a delivery confirmation.
Most operators have 24-72 hours set by default. No further delivery attempts will be made after the validity period expires.

DELETED:

The message was canceled.

The message was canceled.

UNDELIVERABLE:

The message cannot be delivered. Most li...

The message cannot be delivered. Most likely an invalid MSISDN (receiving phone number).

REJECTED:

The mobile network has rejected the mess...

The mobile network has rejected the message. If this message was charged, the charge has failed.

Why do my SMS messages fail to be delivered?

Invalid number:

One of the most common reasons for a fai...

One of the most common reasons for a failed delivery is an invalid number.
A number can be invalid if:

  • The number lacks a country code. GatewayAPI sends text messages to 200+ countries
    and it is therefore necessary to add a country code to make sure that the messages find the right end users.

  • The number is a landline.

  • The end user has changed number and the old number is disconnected.

  • The end user has filled in a wrong phone number
    (this happens more often than you would think).

Carrier filters:

Another common reason for text messages ...

Another common reason for text messages not being delivered is carrier filters.

The specifics vary at implementation, but in general they react to different patterns in the messages. The firewalls and filters have their limitations though. The spammers are continuously changing their approaches and in the pursuit to catch all spam traffic, the carriers sometimes block legitimate traffic as well.

The carrier filters can react, e.g. if many similar text messages are sent to the same number. This is a common occurrence when testing the setup. If text messages are sent on certain days or hours, they can be blocked as well. In France, for example, it is prohibited to send SMS messages for marketing purposes in the evening and during national holidays.

The content of the SMS messages can also cause messages to be blocked. This can happen if the SMS:

  • Lacks clear opt-out instructions.

  • Contains imprecise language with wrong capitalisation and punctuation.

  • Contains certain keywords which may be related to spam, sexual, religious or political content.

  • Includes links in the text. This is not allowed in some countries.

End users:

The end user’s mobile phone can al...

The end user’s mobile phone can also be the culprit. It happens relatively often that the memory of the end user’s mobile phone is full, which means the phone cannot receive the SMS. Your end users could also have firewalls installed on their mobile phones, which can block the SMS. Furthermore, if the end user is traveling in another country, it could lead to the SMS not being delivered, since devices that are roaming are traditionally harder to reach.

Lastly, the end user’s phone can simply be turned off. Carriers will hold text messages for 24-72 hours and if the receiving mobile phone is not turned on within that time frame, the message will expire.

Sender ID:

The Sender ID is the ‘from’ field that i...

The Sender ID is the ‘from’ field that is shown when a message is received. In some countries, such as the US, you can only use numerical characters as the Sender ID whereas in many other countries, it is allowed to use a Sender ID with alphanumeric characters.

Text messages with alphanumeric Sender IDs can be labeled as spam by many carriers though, so we recommend using it with caution and reading up on the restrictions in the country.

Scammers are using social engineering to mask their real identity and to pretend being a trustworthy institution, company or the like, and they do that e.g. by using well known Sender IDs.

What do I have to remember when sending to different countries?

Some countries may have SMS restrictions...

Some countries may have SMS restrictions. It is your responsibility to make sure they are being followed. For that reason we have made a Country SMS Restriction section where you can find information about each country, so you can avoid the SMS messages failing to be delivered.

Can I get a notification when your service is down?

Yes, simply sign up to receive notificat...

Yes, simply sign up to receive notifications regarding maintenance and any incidents that might occur on our status page.

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